He was 11 at the time, but has since turned 12.
The seven other accused are aged between 14 and 29.
Today the court heard evidence from the 22-year-old brother who owns the house where he and his parents and siblings live.
The court was told that the brother had been nominated to supervise the boy because their parents had problems with drug use.
He said he was currently studying full-time at TAFE but needed to find a job to pay the mortgage.
He also admitted he had six prior convictions for driving whilst under suspension or disqualification, and was currently subject to a suspended prison term.
In his ruling, Children’s Court president Denis Reynolds said while he had “no doubt” the brother “had the best intentions and a great amount of loyalty” to his younger brother, he could not be considered under the Bail Act to be a “responsible person”.
Judge Reynolds said the 22-year-old seemed to be under “pressure” himself to find full-time work, and on that basis would be unable to supervise his brother and make sure he goes to school.
Judge Reynolds told the boy’s lawyer that if any further information came to light, they could bring their bail application back to court.
Two other juveniles accused of Mr Slater’s murder, aged 14 and 17, also appeared in the Children’s Court today.
The lawyer for the 17-year-old said her client would be making a bail application later this month.
The lawyer for the 14-year-old told the court he was waiting to speak to his client’s family before deciding if he would apply for bail.
All three juveniles will appear again later this month.